How to check if bit is set in MySQL - php

Question

I have a table in a MySQL database with a BIT(64) row, which is a bitmask of 64 flags.
Using PHP and mysqli, I have an integer $n, which is in the range [0, 64). I have already written a function (see Appendix I) to set the nth bit of a byte array (i.e. string in PHP).
When passing the abovementioned byte-array (string) to MySQL, it seems that bitmask & ?, where ? is mysqli::bind_paramed as the byte array (param type is "s"), does not compare the bits as expected.
For example, using this query:
SELECT id FROM my_table WHERE (bitmask & ?) > 0
upon this table:
CREATE TABLE my_table (id INT PRIMARY KEY, bitmask BIT(64));
How can this be fixed?
I thought of passing a bin2hex and UNHEX() it, but this doesn't seem to fix the problem.
Appendix I
public static function setNthBit(int $n, int $bytes = 8) : string{
$offset = $n >> 3;
$byteArray = str_repeat("\0", $bytes);
$byteArray{$bytes - 1 - $offset} = chr(1 << ($n & 7));
return $byteArray;
}

Answer 1

It appears that the problem originates from that MySQL does not support bitwise comparison of strings. When I pass the bitmask as the parameter directly, MySQL would try to interpret as an integer, e.g. trying to interpret bitmask & '123' as bitmask & 123. I'm unsure how MySQL interprets a bunch of binary characters like \xFF or \x00 -- it just won't work, probably interpreted as 0.
I solved this by passing the bin2hex of the bitmask in the input and then CONV(?, 16, 10) in the query. CONV() will express the data in decimal, which MySQL will interpret as, hopefully, something like a BIGINT, which can be successfully bitwise-compared with a BIT(64) row.